Depending on who is doing the counting, the ancient buildings of Italy span anywhere from 2,500 to 3,000 years old. Whatever the numbers are, they borrow from Etruscan, Greek and Roman influences followed by Gothic, Arabic and Byzantine architecture. The classical Renaissance buildings inspired the Baroque period.

The best evidence to the Etruscans style is in their tombs of the 6th century B.C. that are found in Tuscany, Lazio and Umbria. Their buildings are gone because they were made of wood. However, because of their close cultural and mercantile ties to Greece, they probably would have heavily relied on Greek models. Rome, on the other hand, looked to Etruscan architecture for inspiration, therefore Roman public buildings were primarily Etruscan in style.

The triumphal arches (e.g. Rome's Arch of Constantine, A.D. 313) were typical Roman monuments. They were built to celebrate military victories and were highlighted with reliefs that were usually taken from other monuments. Often times, the adornments depicted episodes from successful battles. The Arch of Constantine was built to celebrate Constantine's victory over co-emperor Maxentius at the Battle of the Milvian Bridge. He attributed the victory to a dream in which he had a vision of the Cross, or still another to a vision where he was told to mark his men's shields with two letters of Christ's name. Yet there are no Christian markings on this 82-feet-tall monument. The Arch of Septimius Severus is the best preserved of the Forum's monuments.

Rome's greatest amphitheater was commissioned in A.D. 72. The Colosseum could hold up to 55,000 people. The Doric, Ionic and Corinthian columns inspired many Renaissance architects who plundered the building, using its travertine marble to build palaces and part of St. Peter's.

The building of domes over square or rectangular spaces was a major development of the Byzantine era (600). The Basilica di San Marco (AD 832-1094) in Venice combines Classical, Romanesque and Gothic architecture, but its key inspiration was Byzantine. The exterior owes its Oriental splendor to treasures from the Republic's overseas empire. The Pentecost Dome showing the descent of the Holy Ghost as a dove, was probably the first dome decorated with mosaics.

Orvieto's duomo displays ornate decorations and sculpture, common to many Romanesque and Gothic cathedrals. Begun in 1290, the duomo was inspired by the Miracle of Bolsena in which real blood from a consecrated host fell on the altar cloth of a church in nearby Bolsena. The duomo, with its breathtaking façade and carvings of scenes from the Old and New Testament, is one of Italy's greatest cathedrals.

The classical ideals of Rome and ancient Greece were reintroduced into Italian architecture during the Renaissance. The basis of Renaissance architecture lies in simple proportional relationships. Brunelleschi's dome for the duomo in Florence, completed in 1436, was a masterpiece of Renaissance design and ingenious engineering. Due to its size, it had to be built without scaffolding. Its orange-tiled dome is Florence's most famous symbol. The city's tallest build is the fourth largest church in Europe. Finished in 1463, the inner shell of the dome forms a platform that supports the outer shell. Bricks were set between 24 marble ribs in a self-supporting herringbone pattern.

Andrea Palladio (1508-80), whose style was imitated in Europe for over two centuries, built Neo-Classical villas and palazzi. The Villa Barbaro at Maser was designed at a time when it was fashionable for the rich of Venice to buy rural estates. With its side wings and linking arcades, these were elegant buildings with the look of a country house. San Giorgio Maggiore (built in 1559) introduced simplicity and portions of Classical architecture to Venice and resembled a Roman temple. The Palazzo Chiericati was a huge mansion borrowed from ancient Romans. The Ca d'Oro, the 15th century House of Gold, reveals a Moorish influence with its roof and pointed arches.

Industrial innovations in glass and metal were applied in new buildings like Mengoni's imposing Galleria Vittorio Emanuele II (1865) in Milan. The galleria has a floor plan in the shape of a Latin cross, with an octagonal center with mosaics representing the four continents of America, Europe, Africa and Asia.

The Mole Antonelliana (1863-1897), designed by Antonelli and topped by a granite spire, was the tallest building in the world when it was built. This building in Turin acts as a signature for the city. It was originally planned to be a synagogue, but when it was finished it was used to house the city's museum. Today it is an exhibition with spectacular views of the city and the Alps.

The Pirelli skyscraper in Milan, built by Ponti and Nervi in the late 1950s, is an example of modern Italian architecture.

Architecture from the last two centuries is best represented in Milan and Turin; and some redevelopment projects have taken place in Genoa.